int redLED = 5;
int greenLED = 4;

void setup() {
  for (int i=4; i<=5; i++){
    pinMode(i, OUTPUT);
  }
}

void loop(){
  digitalWrite(5, HIGH);
  digitalWrite(4, LOW);
  delay(1000);
  digitalWrite(4, HIGH);
  digitalWrite(5, LOW);
  delay(1000);
}

